I’m attempting to automate my backups and it looked like DropDMG would fit in perfectly but I’m running into a problem. Here’s my procedure:
- Backup my boot drive to FireWire drive
- Create a compressed, encrypted disk image of the backup drive
- The dmg goes on one of several firewire drives that I rotate off site
I’ve been using this procedure for about a year and it’s worked out well. I’ve got my boot drive backed up and the data is encrypted so that it’s secure off site.
I’m trying to automate the process so I can just let it run overnight. I’m now using SuperDuper to create the initial backup and then I have it run a shell script when it completes. The shell script contains this command:
dropdmg -g systembackup /Volumes/Backup
the config “systembackup” creates a “.dmg bzip-compressed” image and I’ve got the ecryption passphrase set in there.
I had run some small tests and everything was working fine. SuperDuper did the backup and was able to run the shell script and DropDMG did it’s thing.
I went ahead and had it do the full backup last night but in the morning I found that DropDMG encountered this error:
Error 1 - hdiutil: convert failed - No space left on device for “Backup”
There was 70gb+ on the target disk and the compressed dmg should only be about 30gb.
I started the DropDMG processes again from the Terminal and now I see what’s happening: DropDMG first creates an uncompressed dmg file and then as a separate step it creates a compressed version. Not only does this take a lot of disk space, it also takes a long time to complete. With Disk Utility it will create the compressed dmg reasonably quickly in one step.
What settings do I need to use for DropDMG to get this same, one-step compressed dmg functionality?